Gallium-67 is used medically in tumor-seeking agents. The half-life of gallium-67 is 78.2 hours. If you begin with 36.6 mg of this isotope, what mass remains after 190 hours have passed?

Answer 1

k = 0.693/t_1/2

Substitute k into the following:
ln(36.6/X) = kt
The only unknown is X. Solve for that.

Answer 2

27g